The invention set forth in this specification relates to valve structures which are responsive to an applied force in order to regulate or control hydraulic flow in response to the force. In a sense the valve structures of the invention can be considered as or referred to as fluid or hydraulic amplifiers which are intended to provide servo-type proportional control in accordance with an input force.
It is considered that the nature or character of valve structures in accordance with this invention can be best described by considering a presently intended utilization of these structures. It is considered that they are of primary utility in connection with the operation of controls such as are commonly found in oil refineries. In the past it has been conventional to utilize appropriate electrical controls in connection with refinery operation. It is considered that the use of such electrical controls in refineries is relatively undesirable because of the possibility of such controls causing the explosion of gases which are normally present in and around an oil refinery.
The recognition of the undesirability of using electrical controls in connection with oil refineries has led to the utilization of pneumatic control systems in which air pressure is utilized in connection with conventional valves. While this has been desirable in minimizing the explosion hazards this use of pneumatic control systems has been somewhat undesirable because the valves which have normally been used with such systems have been incapable of being proportionally controlled to comparatively exact control requirements. As a result of this it has been considered that a need existed for new and improved valve structures for use with such pneumatic control systems.